Laser printers print on recording media (for example, sheets of paper) using developers. The laser printer includes a case that stores developer. The case that stores the developer includes a case body. The case body has been formed with an opening. A developing roller is rotatably attached to the case body at a position facing the opening. The developing roller is configured to carry the developer stored within the case body. The laser printer includes a photosensitive member that contacts the developing roller. An electrostatic latent image is formed on a surface of the photosensitive member. The developing roller and the photosensitive member contact each other while rotating, so that the developer carried by the developing roller adheres to the electrostatic latent image on the photosensitive member. Thus, the electrostatic latent image on the photosensitive member is developed with the developer to form a visible image. The developer of the visible image is transferred from the photosensitive member to a recording medium, so that the recording medium is then printed with the developer in the shape of the visible image.
If the developer contained in the case body leaks outside of the case body, devices disposed around the case body may become contaminated. The case body needs to be designed such that the design prevents the leakage of the developer. In a related area, side seal members are used to protect the leakage of the developer from both ends of the developing roller with respect the axial direction of the developing roller. The case body includes an area facing a surface of the developing roller at each end with respect to an axial direction thereof. The side seal members are affixed to the area of the case body and contact the developing roller. Thus, each end of the developing roller is sealed in the developing roller's axial direction.
During operation, the side seal member contacts the developing roller, and a rotation force of the developing roller is transmitted to the side seal member. When the developing roller rotates, the side seal member is pressed inward with respect to the axial direction of the developing roller, and the side seal member is then moved inward. If the side seal member is moved inward, the ability of the side seal member to adequately seal the case may deteriorate. This deterioration increases the likelihood that the developer may leak from the case body.